<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        // 100=>x=>90优秀 90>x>=75不错 75>x>=60及格  60>x 挂科
        var score = prompt("请输入分数");
        // var yx = (100 >= score >= 90);
        var yx1 = score <= 100 && score >= 90;
        // var bc = 90 > score >= 75;
        var bc1 = score >= 75 && score < 90
        // var jg = 75 > score >= 60;
        var jg1 = score >= 60 && score < 75;
        var gk = score < 60;
        
        if(yx1){
            console.log("你很优秀")
        }else if(bc1){
            console.log('非常不错')
        }else if(jg1){
            console.log('及格了')
        }else{
            console.log("挂科了")
        };
    </script>
</body>
</html>